FAQ: I have added double the amount required and the pH is still around 7.8, all that seems to be happening is that the water gets cloudy.

Your water must be very hard (high KH) so you will need to get the KH down to a level where the Neutral Regulator can control the pH. Right now the Neutral Regulator is fighting a losing battle with the high KH. Use Discus Buffer or Acid Buffer to bring the pH down... it will go back up again after a day or so, but add again. Eventually you will get to a point where the pH will take longer and longer to rise again... when that happens use Neutral Regulator to lock in the pH at 7-7.2. Or use an alkalinity test kit, when it gets down to around 1 KH so you can use Neutral Regulator to lock in the pH.